Structure of twins in GaAs nanowires grown by the vapour–liquid–solid process

Semiconducting crystalline materials that are poor conductors of heat are important as thermoelectric materials and for technological applications involving thermal management. A combination of neutron scattering, lowtemperature ultrasonic attenuation and thermal conductivity measurements are reported on single crystals of the semiconductors Sr₈Ga₁₆Ge₃₀ and Ba₈Ga₁₆Ge₃₀. Taken together, these measurements suggest specific structural features that result in a crystal with the lowest possible thermal conductivity, namely that of a glass with the same chemical composition. Weakly bound atoms that 'rattle' within oversized atomic cages in a crystal result in a low thermal conductivity, but the present data show that both 'rattling' atoms and tunnelling states are necessary to produce a true glass-like thermal conductivity.     

Catachrestic Plural Forms. Gregory of Nyssa and Theodore Abū Qurrah on Naming and Counting Essences

The fourth-century thinker and theologian Gregory of Nyssa was a convinced realist about universals. According to him, there is just one substance man for all the individuals of the species man and this universal substance is completely instantiated by each individual. In two of his treatises – the Ad Ablabium and the Ad Graecos – he draws linguistic consequences from this realist position. This enquiry results in the thesis according to which it is incorrect to use natural kind terms (such as names of species) in the plural form, because that would involve stating a plurality of substances, when in fact there is just one substance for all the individuals of a given kind. In consequence, since the substance of all individual human beings is the same, the word ‘man’ can only be used adequately in the singular form. In this contribution, Gregory's reasoning is reconstructed. In the second part of the paper, the posterity of his theory and its endorsement by Theodore Abū Qurrah at the turn of the eighth and ninth centuries are examined.     

Refuge in the Bosoms of the Mountains: A Ninth-Century Muslim Appraisal of Monastic Piety

ABSTRACT

This article examines a relatively little-known text, the Kitāb al-ruhbān/Book of Monks, from the ninth-century Muslim moralist, Ibn Abī al-Dunyā. The topical range of Ibn Abī al-Dunyā’s own literary corpus was extensive, yet the concern for ascetic practices forms a consistent thread throughout his work. As for this particular text, the esoteric wisdom associated with asceticism is specifically communicated through the teachings of Christian hermits. The Kitāb al-ruhbān, formulated as a collection of short dialogues and edifying statements regarding Christian monastic piety, profoundly demonstrates the continuing appreciation for monastic insight, particularly amongst Muslim ascetics, well into the Islamic period. There are, moreover, no explicit traces of sectarianism or confessional barriers here. Instead, the sagacious maxims for maintaining a righteous life are often passed from Christian hermits to devout Muslim listeners. This text thus further reveals the intricate connections between Christian monastic communities and medieval Islamic mystical culture.